Carrier-transmission system



. 1,617,391 J. s. JAMMER CARRIER TRANSMISSION SYSTEM Filed April 9, 1923RBF.

5 LPF cs t m 3 o v Q l I CARRIER i 8 FREQUENCY [L l o i Q I 5 I g:MODULATING g 5 11.! IYIFREQVEMCIESV' I ND I I I I BAND I 1 Li.

FREQUENCY I mike/770K? Jacob J Jammer Patented Feb. 15, i927.

"raranrerrics.

JACOB s. JAMMER, ornnw YORK; N. Y., P NY; moonronatrnn, 013 new YORK,

MTEQ stereos" Assrcn'on T wns'riinn ELECTRIC COIVI- N. Y., A'CORPORATIONOF NEW YORK.

oAnnIEn-TR NsM rssIoN sYsT'iiM, r

n Application filed April,

This invention. relates; to carrier transmission systems, and moreparticularly to carrier telephone systems. I w

An object of the inrention is to supply to a plurality of carriercurrent transmitting channels carrier oscillations ofthe same fre-,

quency from the same f source without interchannel modulation orcross-talk.

Anotherlobject .is to prevent interchannel interference betweentransmitting channels of a carrier telephone system wherein acom- Inonsource. supplies to all channels carrier waves of the same frequency. Iy In accordance w th .tlllS invention the transmitting channels of aplurality of single channel carrier systems supplied'with carrier wavesof: the same frequency from a r nels.

common source are connected to said source by frequency discriminatingmeans tuned to the carrier frequency whereby the currents in one channeldue to modulation are con:

fined to said channel andtherefor'e do not interfere with theoperationof other chan- The inventionwill be described as applied to a pluralityof singlechannel carrier telephone systemsfalthough it will beunderstood that it is also applicabletoa plurality of multiplex carriersystems wherein one channel of, each of the several systems is suppliedwith carrier Waves o-f'the same frequency from a common source.

While the invention is llustrated as applied to carrier transmissionsystems wherein the .unmodulated I carrier components are transmittedfrom the'sending to the receiving terminals, together with the side.hands representing signals it will be evident, of

course, thatit is also applicable to systems operating upon theprinciple of suppression of the uninodulatedcarrier frequency coin-'ponent.

In the drawing:

Fig. 1 illustrates diagrammatically only so much of a plurality ofsingle channel care I rier telephone systems as isnecessary for an lis-a, 's, ea we whi h W. ree we understanding of the invention. r Fig.2is a curve indicating the efficiency ,of the frequency discriminatingmeans connecting the transmitting channels to the common carrier source.I v.

y The :apparatus and circu ts illustrated in Fig..- are located attheijunctions be 1923; serial No; 630,728.

oscillations are to be transmitted and received and correspondinglinesML ML etc, I over which modulated: high frequency oscillationsare to betransmitted and received.

While for the purpose illustration only two sets of coupled low" andhigh frequency lines are shown, it will be understood many more may be,and in practice usually will be,

provided. 7

The illustrated sets offcoupledlow and high frequency lines and thecoupling appa ratus and circuits therefor are exactly alike so adescription of one will sufiice. I

ceiving channels TL and R-L are associated with the 10w frequencyv lineL through transformer 1..

j Thetw o'channelsTL and BL are rendered'substantially conjugat'eby theprovision of an artificial line or ance the line'L l H The transmittingI and receiving channels iet AL tobalQ The high frequency transmittingand rev TL and' RLi, respectively. are connected to t V i the highfrequency lineML through transmitting and receiving band filters TBF,and REF which "separate the outgoing and incoming oscillations.-.Carrier oscillae trons of one frequency! are employed for transmissionin one"direction and v carrier oscillations of another frequency areemployed for transmission in the opposite direction.

These band filters are of the general'type v disclosed. inU. 'S. patentsto George A Campbell Nos. 1,227,113 and,1.227,11& date-:5

May 22, 1917 The transmitting .band'filter 'IBF designed. to passcurrentsof'flthe transmitted carrier frequency and of fife ii n the uppr at-1 W side band and to suppress currents of allwithin either theupper or lower side band and. to suppress currents of all other.frequencies.

The main line ML may, of course, be-utilized for the transmission ofaudio or lower frequency oscillations, high pass and low passrfiltersHPF, and LPF being provided, as shown, to separate the audio and ultraaudio frequency oscillations. v

The transmitting channel TL includes a modulator M and the transmittingband filter TBF previously referred to, the output of the former beingconnected to the latter by a transformer 2.

The modulator M may. be of any well known type, but, as illustrated, isof the three element space current type.

Carrier oscillations of the frequency as signed for outgoingtransmission are supplied to the modulator M, from. a source CS commonto all of the illustrated transmitting channels.

The'low frequency modulating currents from the low frequency line L,delivered by the transformer 1 are impressed upon the input circuit ofthe modulator M, through a transformer 3.

The incoming or receiving channel RL includes the receiving band filterREF a demodulator DM and a low pass filter LPF. The demodulator DM maybe of' any well known type, but, as illustrated, is a three elementrelay of the space current type. The amplitude of the received currentsimpressed upon the demodulator DM is regulated by a potentiometer 4. e

v The low pass filter LPF which is of the general .type disclosed in U.S. patents to George A. Campbell- Nos. 1,227,113 and 1,227,114,isdesigned to passonly currents of the original modulatingfrequenciesand to suppress currents of all other frequencies.

As previously stated, the source CS supplies to each modulator of theseveral illustrated transmitting channelscarrier oscillations ofthe samefrequency.

Since the input circuits of the several modulators are connected inmultiple relatalk.

For such purpose, the carrier supply leads 5 are inductively coupled toeach modulator input circuit by a transformer 6, the primary of which istuned to the carrier fre-' quency currents by'an inductance 7 andcondenser 8 cooperating with suchprimary, and the secondary of whichforms, with variable condenser 9, a loop circuit tuned to the carrier'frequency. v I

This tuned inductive coupling is highly efiicient for the transmissionofcurrents of carrier frequency to which it. is. tuned;.-but issoineflicien't for the transmission of currents of the modulatingfrequencies 1111- pressed'upon the input circuit through transformer 3as to prevent the passage of such modulating currents to the carriersupply leads 5.

Currents of both the carrier frequency and the modulating frequenciesare present in the input circuit ofthe modula'torlvl and some modulationof the carrier currents occurs in the input circuit Therefore there arealso present in the input circuit currents of frequencies within boththe upper and lower side bands of the carrier wave.

If such currents of frequencies within either the; upper or lower sideband are impressed upon the carrier supply leads 5, they will pass intothe input circuits of the modulators of the other transmitting channelsand thereby cause cross-talk between with carrier currents of the samefrequency from the same source are prevented;

F 1g. 2 is an efiiclency curve of the frequency discriminatingcircuitswhich couple the transmitting channels to the carrier currentsupply leads 5. i In this figure, frequencies are plotted againstefficiency of'transmission of currents of the frequencies represented.

Inspection of this eth'ciencycurve shows clearly that the frequencydiscrin'iinating circuits are highly efficient for the transmission ofcurrents of carrier f:.:equcncy and are very inefficient for thetransmission of currents of all other frequencies.

The amplitude of the carrier currents supplied to the input circuits ofthe modulators is regulated by potentiometers 10.

The invention set forth herein is, of course, susceptible of variousother embodiments and adaptations. I

What is claimed is:

1. In a carrier transmission system, the

combination of a plurality of modulators each included in a separatetransmitting channel, a source of carrier currents from which carriercurrents of the same. frequency are supplied to each modulator, means tosupply modulating currents of audio fre- ,quency to each modulator, andmeans comprising a circuit tuned to'currents of carrier llll frequencyconnected in the input, circuit of each modulator and in circuit withsaid source.

2. In a carrier transmlssion system, the

' coinbination'of a source of carrier oscillasame frequency to themodulator of each channel, means to supply modulating currents ft lowerfrequency to each modulator,

and means comprising a circuit sharply tuned to currents of carrierfrequency connected between said source and each modulator.

3. In a-.carrier transmission system, the combination of a plurality ofmodulators, each in a separate transmitting channel, a source of carriercurrents from which carrier currents of the same frequency are suppliedto each modulator, means to supply modulating voice frequency currentsto each modulator, and means to connect said source to the input circuitof each modulator comprising a series circuit and a loop circuitinductively coupled and sharply tuned to currents of the carrierfrequency. g

4. A carrier transmission system comprising a plurality of transmittingchannels, a source of carrier currents from which carrier currents ofthe same frequency are supplied to each channel, means associated witheach channel to modulate in accordance with signals the carrier currentsupplied thereto, and means'to prevent lnterchannel modula- 7 tioncomprising for each channel an inductive coupling between'the' sourceand said modulating means, said couplings being tuned to currents of thecarrler frequency.

5. In a carrier transmission system, the

combination of a plurality of modulators,

each included in a separate transmitting channel, a source of carriercurrents from which carrier currents of the same fre ing circuitstunedto currents of the carrier frequency connecting the modulators tosaid source.

l, 7. A plurality of transmitting circuits, a

common source of oscillation of a single frequency for supplyingsignaling energy to each of said transmitting circuits, and means verysharply selective of oscillations of said single frequency connectingeach of said circuits to said source. i j

v 8. lhe combination of a plurality of modulators each having an inputcircuit and each included in separate transmitting channels adapted forsimultaneous and independent operation, separate sources of modulatingcurrents connected to said input circuits, a source of carrier waves, acommon common supply circuit and each of said modulator input circuits.

9. A. plurality of transmission lines adapted for simultaneous'andindependent operation, a modulator associated with each of said lines, asource of carrier waves, a common supply circuit connecting said source7,

of carrier waves to the input circuits of said fmodulators, wherebycarrier currents of the same frequency are supplied to each modulator,means to supply modulating currents. of audio, frequency to the input ofeach modulator, and frequency discriminating means tuned to the carrierfrequency connectedbetween sa1d common supply c1rcu1t and each of sa1dmodulator input circuits,

whereby the modulating and modulated 'currents in each of said modulatorinput circuits are prevented from entering the other modulator lnputeircults.

.10. In a carrier transmission system, the

combination of a plurality of modulators each having an input clrcuitand each 1ncluded in separate transmitting channels.

adapted for simultaneous and independent operation, separate lowfrequencylines 0011-.

nected to each of said modulator input circuits to supply currents ofaudio frequency thereto, a source of carrier currents, a coma men supplycircuit connecting said source of In witness whereof, I hereuntosubscribe. day of April, A. D., 1923;"

my name this 2d JACOB S. JAMMER.

